CN104090165A - Silicon nano sensing array giant piezoresistive coefficient measuring system and four-point bending force-applying device - Google Patents

Abstract

The invention relates to a silicon nanometer sensor array giant piezoresistive coefficient measurement system and a four-point bending force applying device. The system is composed of three parts: a four-point bending force applying device, a small resistance value detection device and a small strain detection device. Among them, the four-point bending force application device applies uniform axial stress (strain) to the silicon nanowire sensor array chip. type load support platform, nuts, spacers, threaded links, top links, weights of several masses, trays, and loading rams. Weights are added to the tray through the connecting rod on the loading head with adjustable spacing to exert pressure on the silicon nanowires, and the output voltage at both ends of the bridge after pressure is measured through a small resistance detection device. The device of the invention is simple to manufacture, small in volume, low in cost and low in power consumption, and has higher precision and better stability due to the use of array type multi-point average measurement technology.

Description

Silicon nano sensor array giant piezoresistive coefficient measurement system and four-point bending force application device

technical field

The invention belongs to the technical field of micro-nano electromechanical systems, and in particular relates to a silicon nanometer sensor array giant piezoresistive coefficient measurement system. the

Background technique

At present, with the development of micro-nano processing and analysis technologies, it has been found that the size effect, piezoresistive effect, grain boundary effect, etc. It has unique properties, and thus produces powerful and superior micro-nano-scale electronic components, which are widely used in sensors of micro-nano electromechanical systems, such as pressure sensors, acceleration sensors and various biochemical sensors. Therefore, micro-nano materials have great application prospects. The resistance gauge coefficient of silicon varistors with traditional doping process is small. As the size of the sensor becomes smaller, the varistors with traditional doping process can no longer meet the requirements of modern high-sensitivity testing. As a new type of one-dimensional nanomaterial, silicon nanowires have not had a good method to measure the piezoresistive coefficient, an important parameter that characterizes its piezoresistive effect and force-sensitive characteristics, which greatly limits the transmission of silicon nanowires. The application and development of sense structure. The silicon nanowire sensing structure can have a huge piezoresistive coefficient, so the study of the giant piezoresistive coefficient is very meaningful for the practical development of silicon nanowires. At present, when using atomic force microscope (AFM), scanning electron microscope and transmission electron microscope (TEM) to measure the piezoresistive coefficient, it is found that the two ends near the silicon nanowire are in a stretched state, and the middle part is in a compressed state. The two regions are due to the piezoresistive effect. The resulting resistance changes cancel each other out, which greatly reduces the measurement accuracy. Secondly, the method is complex, expensive, and bulky, and has strict requirements on the environment, temperature, and humidity. It is inconvenient to use and takes a long time to measure. the

The piezoresistive detection can also be realized by utilizing the piezoresistive effect of the MOS channel and the junction field effect transistor (JFET) channel. However, there are three main problems in MOS channel piezoresistive detection. (1) The MOS tube is a kind of transistor with amplification effect, and a small change in the gate voltage will cause a significant change in the channel impedance, so the anti-interference ability is poor. (2) In order to realize the piezoresistive detection, it is necessary to connect the MOS tubes into a bridge, and the MOS bridge has negative feedback, which will cause a significant drop in piezoresistive sensitivity. Theoretical calculations show that the sensitivity of the enhanced MOS tube bridge is less than half of that of the force sensitive resistor bridge. (3) When the member is bent, the maximum stress appears on the surface, and the stress decreases rapidly as the depth increases. The structural characteristics of the MOS tube determine that the channel cannot be made on the surface, resulting in a decrease in sensitivity. The JFET channel piezoresistive structure also has problems similar to the MOS channel piezoresistive structure, that is, it is sensitive to gate voltage and has poor anti-interference ability, and the existence of negative feedback will reduce sensitivity. the

Contents of the invention

The present invention aims at the deficiencies of the prior art. The present invention proposes a silicon nanometer sensor array giant piezoresistive coefficient measurement system to achieve the purpose of simplifying the detection device of the giant piezoresistive coefficient and improving the detection sensitivity and precision. The present invention utilizes multiple Multiplexing switches realize the technology of array multi-point average measurement of strain and resistance, so it has higher precision and better stability, easy to use, and shortens the measurement time. the

In order to achieve the above goals, the present invention provides a silicon nano sensor array giant piezoresistive coefficient measurement system, including a four-point bending force application device, a small resistance detection device and a small strain detection device, wherein the four-point bending force application device The force device includes a boat-shaped base 1, base slide rail grooves, nuts 3, two equal-height L-shaped fixtures 4, top connecting rods 5, two equal-height L-shaped load support platforms 12, weights 6, trays 7 and loading pressure heads 8. The front surface of the base 1 is marked with a scale line 2, and the slide rail groove of the base is set on the upper end surface of the base 1; the equal-height L-shaped clamp 4 and the equal-height L-shaped load support platform 12 are respectively opposite It is arranged symmetrically on the centerline of the four-point bending force applying device, and the equal-height L-shaped clamp 4 and the equal-height L-shaped load support platform 12 can be slidably arranged in the slide rail groove of the base; The head 8 is arranged on the top of the equal height L-shaped load support platform 12; the nut 3 includes an upper nut, and the upper nut is arranged between the pallet 7 and the loading head 8, and the top connecting rod 5 is connected from the Pass through the weight 6, the middle part of the tray 7, the upper nut and the middle part of the loading head 8 in order from top to bottom; the ends on both sides of the tray 7 and the loading head 8 respectively abut against the equal-height L-shaped fixture 4 on;

The tiny resistance detection device includes a Wheatstone bridge and a weak signal acquisition system, and the Wheatstone bridge is composed of any silicon nanowire in the silicon nanowire sensing array 13 and the silicon nanowire resistance The same three precision resistors are formed; the weak signal acquisition system includes a preamplifier circuit, a second-stage amplifying filter circuit, a voltage follower, an analog-to-digital converter and a terminal module, and the preamplifier circuit, the second-stage amplifying The filter circuit, the voltage follower, the analog-to-digital converter and the liquid crystal display module are connected in sequence; the weak signal acquisition system is connected with the voltage output end of the Wheatstone bridge;

The micro-strain detection device includes a full-bridge strain gauge 11, and the full-bridge strain gauge 11 is respectively pasted on the force-bearing point positions on the front and back of the silicon nanowire sensor array chip 13, and the four full-bridge Type strain gauges (11) form four strain full-bridge circuits to realize strain multi-point average measurement. The present invention adopts four full-bridge strain gauges (11) to form four strain full-bridge circuits, and the silicon nanowire sensor array chip is There are two on the opposite side, so as to realize the multi-point average measurement of the strain on the silicon nanowire sensor array chip; the weak signal acquisition system is connected with the output end of the strain full bridge circuit.

The present invention also provides a four-point bending force applying device, which includes a ship-shaped base 1, base slide rail grooves, nuts 3, two equal-height L-shaped clamps 4, top connecting rods 5, and two equal-height L-shaped load support platforms 12. Weight 6, tray 7 and loading head 8, the front surface of the base 1 is marked with a scale line 2, and the slide rail groove of the base is set on the upper end surface of the base 1; the contour L-shaped fixture 4 and the equal-height L-shaped load support platform 12 are arranged symmetrically with respect to the center line of the four-point bending force applying device respectively, and the equal-height L-shaped clamp 4 and the equal-height L-shaped load support platform 12 can be slidably arranged on In the slide rail groove of the base; the loading head 8 is arranged on the top of the equal-height L-shaped load support platform 12; the nut 3 includes an upper nut, and the upper nut is arranged on the tray 7 and the loading pressure Between the heads 8, the top connecting rod 5 passes through the weight 6, the middle part of the tray 7, the upper nut and the middle part of the loading head 8 from top to bottom; The parts respectively abut against the said equal-height L-shaped clamps 4 . the

The beneficial effects of the present invention are:

1. The present invention has a large test range for the length of the silicon nanowire sensing array chip subjected to four-point bending, and the length of the silicon nanowire sensing array chip can be a continuously variable size value, and all of them are installed and tested on the same experimental device.

2. The present invention adopts a fixed support platform during the testing process of the silicon nanowire sensor array chip, so that too many influencing factors will not be generated due to the constraints of the fixed end, and the accuracy of the test result is guaranteed. the

3. The present invention can adjust the distance between two support points and two loading points when testing the silicon nanowire sensor array chip, eliminate excessive elongation of the test sample when it is bent under pressure, and improve the accuracy of data. the

4. The present invention adopts a micro-resistance detection device and a micro-strain detection device based on multi-point average measurement technology. The overall device is simple to manufacture, small in size, low in cost, high in precision, low in environmental requirements, and greatly reduced in measurement time , has a strong marketing value. the

Description of drawings

In order to further illustrate the content and characteristics of the present invention, further description in conjunction with the following drawings, wherein:

Figure 1. Schematic diagram of the four-point bending device of the present invention.

Figure 2. Front view of the tested silicon nanowire sensing array. the

Figure 3. Back view of the tested silicon nanowire sensing array. the

Fig. 4. The overall block diagram of the micro-strain detection and micro-resistance detection device of the present invention. the

Fig. 5. A full bridge circuit composed of silicon nanowires of the present invention and three precision resistors with the same resistance value. the

Fig. 6. The multiplexing switch control circuit of the micro-strain detection and micro-resistance detection device of the present invention. the

Figure 7. The preamplifier circuit of the present invention. the

Fig. 8. The second-stage amplification filter circuit and follower circuit of the present invention. the

Fig. 9. A/D conversion circuit of the present invention. the

the

Detailed ways

In order to make the purpose and technical solution of the present invention/the embodiment of the invention clearer, the following will clearly and completely describe the technical solution of the present invention/the embodiment of the invention in conjunction with the accompanying drawings of the present invention/the embodiment of the invention. Apparently, the described embodiments are some of the embodiments of the present invention/invention, but not all of them. Based on the described embodiments of the present invention/invention, all other embodiments obtained by persons of ordinary skill in the art without creative work shall fall within the protection scope of the present invention/invention. the

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention/invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein explain. the

The meaning of "and/or" mentioned in the present invention/invention means that each exists alone or both exist simultaneously. the

The meaning of "inside and outside" in this invention/invention means that relative to the device itself, the direction pointing to the inside of the device is inside, and vice versa is outside, rather than a specific limitation on the device mechanism of the present invention. the

The meaning of "left and right" mentioned in this invention/invention means that when the reader is facing the accompanying drawings, the left side of the reader is the left, and the right side of the reader is the right, rather than the device mechanism of the present invention Specific restrictions. the

The meaning of "connection" in the present invention/invention may be a direct connection between components or an indirect connection between components through other components. the

The meanings of "clockwise" and "counterclockwise" in this invention/invention refer to the clockwise and counterclockwise directions shown in the drawings, which are definitions for the convenience of readers' reading and understanding, not Specific limitations on the device mechanism of the invention/invention. the

Fig. 1 is a schematic view of a four-point bending device of the present invention; Fig. 2 is a front surface view of a measured silicon nanowire sensing array; Fig. 3 is a back view of a measured silicon nanowire sensing array; Fig. 4 is a schematic diagram of the present invention Overall block diagram of micro-strain detection and micro-resistance detection device; Fig. 5 is a full-bridge circuit composed of silicon nanowires of the present invention and three precision resistors with the same resistance value; Fig. 6 is micro-strain detection and micro-resistance detection of the present invention The multiplexing switch control circuit of the device; Fig. 7 is the preamplifier circuit of the present invention; Fig. 8 is the second stage amplification filter circuit and follower circuit of the present invention; Fig. 9 is the A/D conversion circuit of the present invention. The silicon nano sensor array giant piezoresistive coefficient measurement system provided by the present invention includes three parts: a four-point bending force applying device, a small resistance value detection device and a small strain detection device. Among them, the four-point bending force application device applies uniform axial stress (strain) to the silicon nanowire sensor array chip. As shown in Figure 1, the device includes a boat-shaped base 1, a slide rail groove on the base, and a mirror-placed contour L-shaped fixture. 4. Contoured L-shaped load support platform 12 , nut 3 , spacer 9 , threaded connecting rod 10 , top connecting rod 5 , several weights 6 , tray 7 and loading head 8 placed in mirror image. The assembly steps of the four-point bending device are described in detail below:

(a) The L-shaped clamps 4 of equal height placed in the mirror image slide in the slide rail grooves above the base respectively, insert the threaded connecting rod 10, put on the gasket 9, and then screw on the nut 3, do not tighten it temporarily, according to the loading pressure head 8 Use the scale line 2 on the front surface of the base 1 to symmetrically adjust the mirrored L-shaped fixture 4 to the designated position, and tighten the nut 3 to make the L-shaped fixture 4 and the base 1 tightly connected;

(b) Insert the threaded connecting rod 10 into the L-shaped load support platform 12 placed in the mirror image, put the gasket 9 on it, and then screw on the nut 3, do not tighten it temporarily, depending on the length of the silicon nanowire sensor array chip 13 In the case of , use the scale line 2 on the front surface of the base 1 to symmetrically adjust the mirrored L-shaped load support platform 12 of equal height to the designated position, and tighten the nut 3 so that it is firmly connected with the base 1;

(c) By adding a weight 6 to the tray 7 loaded with the indenter 8, causing the chip to be subjected to axial uniform stress, a four-point bending test can be carried out.

The following describes the giant piezoresistive coefficient detection process of the four-point bending loading device provided by the present invention and the four-point bending test of silicon nanowires, which is specifically completed by the following steps:

The strain measuring method adopted in the present invention is based on a resistance strain gauge, which converts the strain into an electrical signal for measurement. That is, the stress point of the silicon nanowire sensing array chip 13 is closely attached to the strain gauge 11. The effect is that when the silicon nanowire sensing array chip 13 is deformed to a certain degree, the strain gauge 11 will also produce a corresponding equivalent strain. Output a voltage signal proportional to the strain, and use the PC host computer for data processing to obtain the strain value of the silicon nanowire sensor array. Its working process is as follows: the silicon nanowire sensor array is compressed to produce axial strain → the resistance value of the strain gauge changes → the output voltage of the full bridge changes → small signal amplification → data processing → recording relevant strain data. In order to improve the strain measurement accuracy of silicon nanowires, the present invention adopts the strain gauge Wheatstone full-bridge method, which has the characteristics of high sensitivity, wide measurement range, simple circuit, high precision and easy temperature compensation, etc., which satisfies the strain well. measurement requirements. The 5V supply voltage of the strained full bridge adopts ADP3303;

Sticking the strain gauge is the most important part. During the measurement process, in order to transmit the deformation of the silicon nanowire sensor array to the strain gauge through the bonding layer, it is necessary to ensure that the bonding layer is uniform, firm and free of creep. . The pasting process is: check the resistance value of the strain gauge → clean the surface of the silicon nanowire sensor array chip → paste the strain gauge → cure → measure the insulation resistance of the strain gauge → lead out the wire;

A plurality of strain gauge conductive adhesives and terminals of strain gauges are connected to a weak signal acquisition system through a multiplexing switch to form a micro strain detection device through Dupont wires. Specifically, because the differential mode strain signal output by the bridge is very small, based on the characteristics of the signal, the present invention adopts AD620, an instrument integrated operational amplifier produced by AD Company. AD620 has low power consumption, adjustable gain, high input impedance and common mode The instrument amplifier with rejection ratio is especially suitable for small signal preamplification stage. OP07 has low input offset voltage, low temperature drift, low input noise, voltage amplitude and long-term stable high-precision operational amplifier. Through the amplification circuit, the weak small signal of the bridge is amplified and filtered by cascading; the A/D converter is the core component of the data acquisition circuit, which is responsible for converting the input analog signal into a digital signal for processing by the central processing unit . The correct choice of A/D converter is the key to improving the accuracy of the data acquisition circuit. The AD7794 used in the present invention is a high-resolution analog-to-digital converter introduced by ADI. The AD7794 is suitable for low power consumption, low noise, and complete analog front-end in high-precision measurement applications. It has a built-in low-noise 24-bit 6-way differential input. ; It also integrates an on-chip low-noise instrumentation amplifier, so small signals can be directly input to the ADC. A precision low-noise, low-temperature drift bandgap reference voltage source is built-in on-chip, and up to two external differential reference sources can also be used. On-chip features include programmable excitation current source, fuse current control and bias voltage generator. The terminal power switch can be used to turn off the bridge sensor between two conversions, thereby minimizing the system function, the output rate can be changed in the range of 4.17HZ to 470HZ, the power supply voltage is 2.5V to 5.25V, and its clock The signal port, the data writing port and the data output port are respectively connected to PA3, PA5, and PA6 of the low-power-consumption single-chip microcomputer STM32F103RBT6. AIN1+ and AIN1- of AD7794 are used to collect the analog voltage output by the bridge, the reference source is REF1+ and REF1-, and the data can be saved in EEPROM after A/D analog-to-digital conversion; in terms of data processing, the EEPROM module stores more data , choose the AT24C256 storage device with larger storage space and lower cost. This EEPROM has a capacity of 32KB and is connected to STM32 through the I ² C bus to realize data storage and reading. RS232 realizes the communication work with the upper computer, and successfully transmits a large amount of test data to the PC for data processing and analysis. Of course, the value can also be displayed intuitively on the LCD1602 liquid crystal.

When the bridge is in a balanced state, △Usc=0, and when the silicon nanowire sensing array is under pressure, the strain of the strain gauge changes, resulting in a change of △Usc. According to the formula ε=△Usc/(Ui*K), the strain value of the silicon nanowire sensing array after compression can be calculated. the

Among them: ε——the strain value of the silicon nanowire after compression;

      △Usc——The output voltage of the full bridge after the strain gauge is compressed;

                                                                   

K——The sensitivity coefficient of the strain gauge.

In order to ensure more accurate data, the multiplexer switch CD4052 is externally connected to the full bridge circuit of multiple strain gauges. CD4052 is a differential 4-channel digital control analog switch with two binary control input terminals A and B and INH input. It has low on-resistance and very low off-leakage current. A digital signal with an amplitude of 4.5 to 20V can control an analog signal from peak to peak to 20V. For example, if VDD=+5V, VSS=0, VEE=-13.5V, then the digital signal of 0~5V can control the analog signal of -13.5~4.5V, these switching circuits are in the whole VDD-VSS and VDD-VEE power supply range It has extremely low static power consumption and has nothing to do with the logic state of the control signal. When the INH input = "1", all channels are cut off. A 2-bit binary input signal strobes one of 4 pairs of channels that connect the input to the output. The present invention uses the second Y channel, and connects the control bits A and B to PA1 and PA2 of the STM32 to set them to 1 and 0. Average the values of each channel of the multiplexing switch CD4052, record the average strain value for subsequent data processing;

Since △R/R is very small, the measurement of the multimeter is not very accurate, and some measurement circuits are needed to convert the measurement of the relative change of resistance △R/R into the measurement of voltage, through the formula △Uout=(△R/R)*U0 , the small change in the resistance value of the silicon nanowire 13 can be calculated conveniently.

Among them: △Uout——bridge output voltage;

          U0——power supply voltage (for bridge voltage);

      △R/R——The ratio of the resistance value change of the silicon nanowire after compression to the resistance value before compression.

A typical measurement circuit uses a Wheatstone bridge. Due to the silicon nanowires being squeezed and strained, the resistance value changes, which causes the imbalance of the bridge and generates a differential signal. The input stage impedance of the DC amplifier is very high, and its load impedance can be regarded as infinite compared with the bridge wall impedance. Therefore, the present invention adopts a direct current bridge, a Wheatstone full-bridge circuit composed of any silicon nanowire in the silicon nanowire sensing array 13 and three precision resistors with the same resistance value, and measures the change of its resistance value when strain occurs;

The present invention utilizes a multiplex switch CD4052 to form a small resistance value detection device with a plurality of Wheatstone bridges and a weak signal acquisition system, and averages a plurality of measured values. Its pre-amplification circuit is also built by AD620, and the second-stage output stage amplifier circuit is also built by OP07. In order to suppress interference, the first stage is used as a first-order low-pass filter. In order to improve the driving ability and ensure that the signal does not There will be too much attenuation in the front amplifier, and the last stage is used as a voltage follower; the A/D converter of the tiny resistance detection device also uses the low power consumption, low noise, and high resolution AD7794 analog-to-digital conversion in high-precision measurement applications device. The average voltage value of the final output is displayed on the liquid crystal LCD1602. The array multi-point average measurement technology is adopted to improve the measurement accuracy of the resistance change.

According to the scale line 2 on the front surface of the base 1, symmetrically adjust the distance between the top points of the mirrored (two opposite) L-shaped load support platforms 12 of equal height, tighten the nut 3, fix it on the base 1, and then The silicon nanowire sensor array chip 13 is placed on the support platform 12 to ensure that the silicon nanowire 13 is horizontally flat and vertical, and that the load of the loading indenter 8 acts on the designated position, ensuring the accuracy and stability of loading;

The loading indenter first places the two pressure points of the loading indenter on the surface of the silicon nanowire sensor array chip 13 through the slide rails on both sides of the equal-height L-shaped fixture 3 placed in mirror image (two opposites), and passes through the loading indenter 8 The upper connecting rod 5 adds some weights 6 to the tray 7 to apply pressure to the surface of the silicon nanowire sensing array chip 13;

Slowly add weights, and when running the loading head 8, record the averaged strain and resistance value changes of the silicon nanowire sensing array 13, and use the general piezoresistive coefficient formula to realize silicon nanowire sensing according to the strain and resistance value changes Calculation of the giant piezoresistive coefficient of the array.

The above are only specific embodiments of the present invention, and do not limit the application of the present invention to the measurement of piezoresistive coefficients of other materials. All modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall include Within the protection scope of the present invention. the

The above is only the embodiment of the present invention/invention, and its description is relatively specific and detailed, but it should not be construed as limiting the patent scope of the present invention/invention. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention/invention. the

Claims (10)

1. A silicon nano sensor array giant piezoresistive coefficient measurement system, characterized in that it comprises a four-point bending force application device, a tiny resistance value detection device and a small strain detection device, wherein, The four-point bending force application device includes a boat-shaped base (1), a base slide rail groove, a nut (3), two equal-height L-shaped clamps (4), a top connecting rod (5), two equal-height L-shaped loads Supporting platform (12), weights (6), tray (7) and loading pressure head (8), the front surface of the base (1) is marked with a scale line (2), and the slide rail groove of the base is set on the The upper end surface of the base (1); the equal-height L-shaped clamp (4) and the equal-height L-shaped load support platform (12) are respectively arranged symmetrically with respect to the center line of the four-point bending force applying device, and the The contour L-shaped clamp (4) and the contour L-shaped load support platform (12) can be slidably arranged in the slide rail groove of the base; the loading head (8) is arranged on the contour L-shaped load support The upper part of the platform (12); the nut (3) includes an upper nut, the upper nut is arranged between the tray (7) and the loading head (8), and the top connecting rod (5) is from the top to pass through the weight (6), the middle part of the tray (7), the upper nut and the middle part of the loading head (8) in turn; the ends of the tray (7) and the loading head (8) respectively abut on the contour L-shaped fixture (4); The micro-resistance detection device includes a Wheatstone bridge and a weak signal acquisition system, and the Wheatstone bridge is composed of any silicon nanowire in the silicon nanowire sensing array (13) and the silicon nanowire Three precision resistors with the same resistance value; the weak signal acquisition system includes a preamplifier circuit, a second stage amplifying filter circuit, a voltage follower, an analog-to-digital converter and a terminal module, the preamplifier circuit, the second The stage amplification filter circuit, the voltage follower, the analog-to-digital converter and the liquid crystal display module are connected in sequence; the weak signal acquisition system is connected with the voltage output end of the Wheatstone bridge; The micro-strain detection device includes a full-bridge strain gauge (11), and two pieces of the full-bridge strain gauge (11) are respectively pasted on the front and back of the silicon nanowire sensing array chip (13) at the stress point position , the four full-bridge strain gauges (11) form four full-strain bridge circuits; the weak signal acquisition system is connected to the output end of the full-strain bridge circuit. 2. A silicon nanometer sensor array giant piezoresistive coefficient measurement system according to claim 1, characterized in that, the nut (3) also includes a middle nut and a side nut, which are respectively used to divide the contour The L-shaped load support platform (12) and the equal-height L-shaped clamp (4) are fixed in the slide rail groove; the ends of the middle nut and the side nut are respectively provided with threaded connecting rods (10), and are connected with the equal height A gasket (9) is arranged between the L-shaped load supporting platform (12) and the L-shaped fixture (4) of equal height. 3. A silicon nanometer sensor array giant piezoresistive coefficient measurement system according to claim 2, characterized in that it also includes a silicon nanowire sensor array chip (13), and the contour L-shaped load support platform ( 12) are respectively provided with a triangular pointed tip, and the silicon nanowire sensor array chip (13) is placed on the triangular pointed tip; the bottom of the loading pressure head (8) has two detachable side triangular pointed tip, the equilateral triangular pointed tip can be movably arranged on the top of the equal-height L-shaped load support platform (12), and is symmetrically distributed at the zero point position in the middle of the scale line (2); The triangular pointed tip is arranged between the loading pressure head (8) and the silicon nanowire sensing array chip (13). 4. A silicon nanometer sensing array giant piezoresistive coefficient measurement system according to claim 2 or 3, characterized in that the connecting rod part of the top connecting rod (5) is threaded. 5. A silicon nanometer sensor array giant piezoresistive coefficient measuring system according to claim 1, characterized in that, the bridge supply voltage of the Wheatstone bridge is provided by a precision voltage source. 6. A silicon nanometer sensor array giant piezoresistive coefficient measurement system according to claim 5, wherein the terminal module is a liquid crystal display or a host computer. 7. a kind of silicon nano sensor array giant piezoresistive coefficient measurement system according to claim 5 or 6, is characterized in that, comprises a plurality of Wheatstone bridges, and described a plurality of Wheatstone bridges are made up of a plurality of resistance values It is composed of the same silicon nanowires and precision resistors; multiple reset switch control circuits are arranged between the multiple Wheatstone bridges and the weak signal acquisition system. 8. A four-point bending force application device, characterized in that it includes a boat-shaped base (1), a base slide rail groove, a nut (3), two equal-height L-shaped clamps (4), a top connecting rod (5), Two equal-height L-shaped load support platforms (12), weights (6), trays (7) and loading pressure heads (8), the front surface of the base (1) is marked with a scale line (2), and the The slide rail groove of the base is set on the upper end surface of the base (1); the equal-height L-shaped clamp (4) and the equal-height L-shaped load support platform (12) are respectively relative to the center of the four-point bending force applying device. Line symmetrical arrangement, and the equal-height L-shaped clamp (4) and the equal-height L-shaped load support platform (12) can be slidably set in the slide rail groove of the base; the loading head (8) is set on the The upper part of the equal-height L-shaped load support platform (12); the nut (3) includes an upper nut, and the upper nut is arranged between the pallet (7) and the loading head (8), and the top is connected The rod (5) passes through the weight (6), the middle part of the tray (7), the upper nut and the middle part of the loading head (8) from top to bottom; the tray (7) and the loading head (8) The ends on both sides respectively abut against the said equal-height L-shaped clamp (4). 9. A four-point bending force applying device according to claim 8, characterized in that, the nut (3) also includes a middle nut and a side nut, which are respectively used to support the equal-height L-shaped load platform (12) and the equal-height L-shaped clamp (4) are fixed in the slide rail groove; the ends of the middle nut and the side nut are respectively provided with threaded connecting rods (10), and are connected with the equal-height L-shaped load support platform A gasket (9) is arranged between (12) and the equal-height L-shaped clamp (4). 10. A four-point bending force applying device according to claim 9, characterized in that it further comprises a silicon nanowire sensor array chip (13), and the tops of the equal-height L-shaped load support platform (12) are respectively A triangular pointed tip is provided, and the silicon nanowire sensing array chip (13) is placed on the triangular pointed tip; the bottom of the loading indenter (8) has two detachable equilateral triangular pointed tips, The equilateral triangular pointed points are movably arranged on the top of the equal-height L-shaped load support platform (12), and are symmetrically distributed at the middle zero position of the scale line (2); the equilateral triangular pointed points are arranged Between the loading pressure head (8) and the silicon nanowire sensing array chip (13).